JP2007095976A - Semiconductor device reworking method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To efficiently rework a memory module in a short period of time without affecting good-quality semiconductor memories. <P>SOLUTION: A heated solder melting line 4 is pressed against a row of solder balls 2b formed to one side of a removing semiconductor memory 2, when reworking the semiconductor memory 2 in the memory module 1. The solder balls 2b are melted and cut by locally heating the solder balls 2b after moving the solder melting line 4 in parallel with a mounting face of a module wiring board 3. The solder melting line 4 is composed of two lines of a high-temperature line and a low-temperature line having a heat-generation temperature lower than that of the high-temperature line. The melt solder balls 2b are made into contact with the low-temperature line after bringing the high-temperature line into contact with the solder balls 2b first. By this, it is possible to prevent the solder balls 2b from being rejoined after melting by the high-temperature line. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a rework technique for a semiconductor device, and more particularly to a technique effective for reworking a semiconductor memory mounted on a memory module.

  In memory modules used for expansion memories such as personal computers and workstations, so-called actual machine selection, in which the memory module is mounted on a personal computer or the like for selection, is widely performed.

  In general, a memory module has a plurality of semiconductor memories mounted on a printed wiring board in order to cope with an increase in the capacity of the memory. For example, a package such as BGA (Ball Grid Array) is used.

  In recent years, due to the increase in the speed of semiconductor memories, the failure rate of memory modules in actual machine selection tends to increase. Therefore, in the memory module, so-called rework is indispensable to replace a semiconductor memory that has become defective due to selection of actual devices.

  As a rework technique of the memory module, for example, a hot air method and a heat tool method are known. The hot air system is a system in which hot air is applied from the side of a package of a semiconductor memory mounted on a printed wiring board, and the solder is melted to remove the package.

  The heat tool method is a method in which a heat tool such as a heater is brought into close contact with the upper surface of the package of the semiconductor memory, and the solder is melted and removed by the heat conduction.

  However, the present inventors have found that the rework technology in the memory module as described above has the following problems.

  In the rework technology using the hot air method, there is no room for a rework nozzle that ejects hot air when the mounting density of the semiconductor memory is high, and there is a possibility that the rework cannot be performed.

  Moreover, the non-defective semiconductor memory mounted in the periphery by the hot air is also heated, which may cause the non-defective semiconductor memory to be deteriorated.

  On the other hand, in the heat tool method, since the heat tool is closely attached to the upper surface of the package, it can be used even when the mounting density of the semiconductor memory is high, and the influence on the peripheral non-defective semiconductor memory can be suppressed. Since heating is performed from the upper surface, there is a problem that the time until the solder is melted becomes longer, and the working efficiency is greatly reduced.

  An object of the present invention is to provide a technique capable of efficiently reworking a memory module in a short time without affecting a good semiconductor memory.

  The above and other objects and novel features of the present invention will be apparent from the description of this specification and the accompanying drawings.

  Of the inventions disclosed in the present application, the outline of typical ones will be briefly described as follows.

  The present invention is a method for reworking a semiconductor device mounted on a printed circuit board, having a semiconductor chip mounted on the main surface of the circuit board, and arranging connection electrodes on the back surface of the circuit board as external terminals. The connecting electrode melted wire is pressed against the electrode to melt and cut the connecting electrode, and the semiconductor device mounted on the printed wiring board is removed.

  Moreover, the outline | summary of the other invention of this application is shown briefly.

  In the present invention, the connection electrode melting line is composed of a first connection electrode melting line and a second connection electrode melting line having a temperature lower than that of the first connection electrode melting line, and the cutting direction. On the other hand, after the first connecting electrode melting line comes into contact with the connecting electrode, the second connecting electrode melting line is arranged so as to come into contact with the connecting electrode. By preventing the second connecting electrode melted line from coming into contact with the cut surface of the connecting electrode melted by the wire, refusion of the cut surface of the connecting electrode melted by the first connecting electrode melted wire is prevented. is there.

  According to the present invention, the semiconductor device includes a volatile semiconductor memory, and the printed wiring board includes a plurality of volatile semiconductor memories to constitute a memory module.

  Furthermore, according to the present invention, the semiconductor device to be reworked is determined to be defective in the screening test.

  Among the inventions disclosed in the present application, effects obtained by typical ones will be briefly described as follows.

  (1) Since the connection electrode can be locally heated, thermal stress on the peripheral semiconductor device mounted on the printed wiring board can be reduced.

  (2) In addition, the semiconductor device can be efficiently removed in a short heating time, and the reworking time can be greatly shortened.

  (3) According to the above (1) and (2), it is possible to reduce the manufacturing cost of a product such as a memory module configured using a semiconductor device.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Note that components having the same function are denoted by the same reference symbols throughout the drawings for describing the embodiment, and the repetitive description thereof will be omitted.

  FIG. 1 is a side view of a memory module when reworking a semiconductor memory using a solder melting line according to an embodiment of the present invention, and FIG. 2 is a top view of the memory module when reworking the semiconductor memory using a solder melting line. FIG. 3 is a side view of a semiconductor memory in which a part is enlarged at the time of rework using a solder melting line, and FIG. 4 shows a part of the semiconductor memory in which solder balls are cut by the melting line in FIG. It is sectional drawing.

  In the present embodiment, the memory module 1 is used for an extended memory such as a personal computer or a workstation. As illustrated in FIG. 1, the memory module 1 includes a plurality of semiconductor memories (semiconductor devices) 2 and a module wiring board (printed wiring board) 3.

  The semiconductor memory 2 is composed of a volatile semiconductor memory, such as a DRAM (Dynamic Random Access Memory), which is quite a BGA type package.

  In the semiconductor memory 2, for example, a semiconductor chip is mounted on the main surface of a printed wiring board 2a made of glass epoxy resin or the like via an adhesive such as an insulating resin. In addition, connection electrodes and a wiring pattern arranged in an array are formed on the back surface of the printed wiring board 2a.

  These connection electrodes are respectively formed with solder balls (connection electrodes) 2b made of spherical solder. The main surface of the semiconductor chip and the printed wiring board 2a is sealed with a sealing resin 2c to form a package.

  The module wiring board 3 is a printed mounting board on which the semiconductor memory 2 is mounted. The semiconductor memory 2 is mounted on the front surface and the back surface of the module wiring board 3 in the longitudinal direction of the module wiring board 3.

  The semiconductor memory 2 is mounted on the module wiring board 3 by electrically mounting the semiconductor memory 2 on electrodes such as lands formed on the module wiring board 3 by superposing the solder balls 2b and performing reflow. Connecting.

  For example, the memory module 1 actually mounts the memory module 1 in a personal computer or the like, and sorts out defective semiconductor memories in actual machine sorting for sorting out non-defective / defective products of the semiconductor memory 2. Thereafter, rework (reproduction) of the defective semiconductor memory is performed.

  When reworking the memory module 1, the molten wire (connecting electrode molten wire) 4 is applied to the solder ball 2b formed on the back surface of the printed wiring board 2a and cut while melting the solder ball 2b. Then, it is removed from the module wiring board 3.

  The melt wire 4 that melts and cuts the solder ball 2b is made of, for example, a heating wire, and causes the solder melt wire 4 to generate heat by passing an electric current or the like. The melt line 4 is at least about the same length as one side of the package, and is configured in a substantially straight line in a tensioned state.

  FIG. 2 is a top view of the memory module at the time of reworking the semiconductor memory 2 using the solder melting line 4, and FIG. 3 is a side view of the semiconductor memory 2 in which a part is enlarged at the time of reworking using the solder melting line 4. FIG.

  At the time of reworking, first, the heated solder melting line 4 is pressed against a row of solder balls 2b formed on one side of the semiconductor memory 2 to be reworked. Then, the solder fusion wire 4 is moved in parallel with the mounting surface of the module wiring board 3 from one side of the semiconductor memory 2 to the other side opposite to the semiconductor memory 2 (FIG. 3, cutting direction).

  As a result, the solder ball 2b in contact with the solder melting line 4 is locally heated and melted and sequentially cut.

  FIG. 4 is a cross-sectional view showing a part of the semiconductor memory 2 in which the solder balls 2b are cut by the fusion line 4 of FIG.

  As shown in FIG. 4, the solder melting line 4 includes a high temperature line (first connection electrode melting line) 4a and a low temperature line (second connection electrode melting line) 4b having a lower heating temperature than the high temperature line 4a. It is comprised from two. The high temperature line 4a and the low temperature line 4b are located in parallel to the cutting direction. At the time of cutting, the high temperature line 4a first contacts the solder ball 2b, and then the solder ball 2b melted by the high temperature line 4a. Is formed in contact with the low-temperature line 4b.

  In this case, after the solder ball 2b is completely melted by the high temperature wire 4a, the molten solder ball 2b is solidified to some extent by bringing the low temperature wire 4b into contact with the melted solder ball 2b. The subsequent recombination of the solder balls 2b can be prevented.

  As a result, according to the present embodiment, in the rework of the semiconductor memory 2, only the solder ball 2 b can be heated by the heated portion, so that the thermal stress of the non-defective semiconductor memory 2 can be greatly reduced. .

  Further, by locally heating the solder balls 2b, the semiconductor memory 2 can be efficiently removed in a short heating time, and the reworking time can be greatly shortened.

  Further, in the present embodiment, the case where the solder melting line 4 is composed of the high-temperature line 4a and the two high-temperature lines 4a has been described. However, the solder melting line 4 is the solder ball 2b of the semiconductor memory 2 during rework. As long as they do not recombine, any configuration may be used, for example, a single heat wire may be used.

  As mentioned above, the invention made by the present inventor has been specifically described based on the embodiment. However, the present invention is not limited to the embodiment, and various modifications can be made without departing from the scope of the invention. Needless to say.

  The present invention is suitable for a rework technique of a defective semiconductor memory mounted on a memory module.

It is a side view of a memory module at the time of rework of a semiconductor memory using a solder fusion line by an embodiment of the invention. It is a top view of a memory module at the time of rework of a semiconductor memory using a solder melting line. FIG. 3 is a side view of a semiconductor memory in which a part thereof is enlarged at the time of rework using a solder melting wire. FIG. 4 is a cross-sectional view showing a part of the semiconductor memory 2 in which a solder ball is cut by a fusion line 4 in FIG. 3.

Explanation of symbols

1 Memory Module 2 Semiconductor Memory (Semiconductor Device)
2a Printed wiring board 2b Solder ball (connection electrode)
2c Sealing resin 3 Module wiring board (printed wiring board)
4 Solder melt wire (Connecting electrode melt wire)
4a High-temperature wire (first connecting electrode melting wire)
4b Low temperature wire (second connecting electrode melting wire)

Claims (4)

A method of reworking a semiconductor device mounted on a printed circuit board, having a semiconductor chip mounted on the main surface of the circuit board, and arranging connection electrodes on the back surface of the circuit board as external terminals,
A semiconductor device characterized in that the connecting electrode melting line is pressed against the connecting electrode to melt and cut the connecting electrode, and the semiconductor device mounted from the printed wiring board is removed. Rework method. In the rework method of the semiconductor device according to claim 1,
The connection electrode melting line is
A first connecting electrode melt wire;
The second connection electrode melting line having a temperature lower than that of the first connection electrode melting line,
With respect to the cutting direction, after the first connection electrode melt line contacts the connection electrode, the second connection electrode melt line is arranged to contact the connection electrode,
The connection electrode melted by the first connection electrode melting wire by bringing the second connection electrode melting wire into contact with a cut surface of the connection electrode melted by the first connection electrode melting wire. A rework method for a semiconductor device, characterized by preventing refusion of cut surfaces of electrodes. In the rework method of the semiconductor device according to claim 1 or 2,
The semiconductor device is a volatile semiconductor memory,
A method of reworking a semiconductor device, wherein the printed wiring board includes a plurality of the volatile semiconductor memories to constitute a memory module. In the rework method of the semiconductor device according to any one of claims 1 to 3,
A semiconductor device rework method, wherein the semiconductor device to be reworked is a semiconductor device determined to be defective in a screening test.

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